Understanding Columnstore Indexes in SQL Server Part 3
My last two blogs were on understanding columnstore and creating columnstore indexes. In this post, I will touch on one last topic, when to use columnstore indexes. As noted in my prior posts these indexes are designed for large data warehouse workloads, not normal OLTP workload tables. As with any index design it is important to know your data and what you will be using the data for. Be sure to look to what types of queries you will be running against it, as well as how the data is loaded and maintained. Let’s look at a few questions you… Continue reading
Understanding Columnstore Indexes in SQL Server Part 2
In my last blog I explained what a columnstore index is, in this blog, we will dive into creating a clustered columnstore index and look at the performance differences the index can make. Let’s get started. Using AdventureworksDW2016CTP3 we will work with the FactResellerSalesXL table which has 11.6 million rows in it. The simple query we will use as a demo just selects the ProductKey and returns some aggregations grouping them by the different product keys. First, we will run the query with no existing columnstore index and only using the current clustered rowstore (normal) index. Note that I turned… Continue reading
Understanding Columnstore Indexes in SQL Server Part 1
Recently I reviewed filtered indexes, this time let’s look at columnstore indexes. These indexes are very useful for data warehouse workloads and large tables. They can improve query performance by a factor of 10 in some cases, so knowing and understanding how they work is important if you work in an environment with larger scaled data. Now, I admit when these first were introduced in SQL Server 2012 I found them very intimidating (additionally, you couldn’t update them directly). For me, anytime you say columnstore, my mind tends to set off alarms saying wait stay away, this is too complicated.… Continue reading
Comparing Execution Plans
When you run a query twice, and get dramatically different run times, your first step can be to try to identify the differences in execution plans. For many that means running the two different queries (before & after) and splitting you screen in order to visually compare the plans. Did you know SQL Server Management Studio gives you the option to compare to different execution plans? It makes it easy not only to visualize the differences, but it also shows you detail properties that allow you to dive into the numbers. This functionality was introduced with SQL Server 2016, and… Continue reading